Such a machine is disclosed, for example, in German Patent Document No. DE-A1-43 22 268, related to U.S. Pat. No. 5,442,249, both of which are incorporated by reference herein.
It has long been known to mount the laminated stator part of a larger horizontal-axis electrical machine in a number of retaining rings, which are arranged one behind the other in the axial direction, are spaced apart from one another and are each fixed on two opposing sides by means of a retaining structure to the base frame or base below. A machine having such a design is disclosed, for example, in Swiss Patent Document CH-A5-665 507, related to U.S. Pat. No. 4,669,553, both of which are incorporated by reference herein. It is characterized in that any oscillations and thermal stresses are kept low during operation. The known means for fixing the laminated stator part allow for simple assembly, easy accessibility of the structural parts to be welded and ensure the good quality of the welding seams.
In the case of very large air-cooled turbogenerators, the double-frequency oscillations of the laminated core and the resulting acoustic emissions are very high. However, as the size of the machine increases, the loads on the components and on the welding seams at the points of connection to the housing also increase. The oscillations of the laminated core and thermal cycling may result in fatigue phenomena and fissuring. It is therefore proposed in the specification mentioned initially, DE-A1-43 22 268, to simply fix the laminated stator part or built-in stator with its retaining rings in the horizontal direction in a resilient manner to the base frame or housing. This is achieved by leaf springs being built-in in the laterally arranged retaining structures of the retaining rings. Both ends of the perpendicular leaf springs are welded to the retaining rings. In the freely flexible central region, the leaf springs are welded to the housing by means of a number of tubular pieces arranged one on top of the other. As a result, given high strength in the circumferential direction, the housing is isolated acoustically and in terms of oscillations from the laminated stator part, as long as the oscillation amplitudes are on a horizontal plane.
One disadvantage of the known manner of mounting the built-in stator, however, is that, when there are different types of oscillations of the built-in stator, in which vertical components occur, isolation is only effected to a limited extent.